The study, which was published in the journal Pediatrics, chronicled the bedtimes of 977 healthy preschool children aged 3 to 5 taking part in the Study of Early Childcare and Youth Development. The children were split into three groups: one-quarter went to bed at 8 p.m. or earlier; one-half went to bed between 8 p.m. and 9 p.m.; and one-quarter went to bed after 9 p.m.

After revisiting the subjects 10 years later when they reached ages 13 to 15, the researchers found that those with the earliest bedtimes—8 p.m. or before—were the least likely to be obese as teenagers. In contrast, 16 percent of the kids in the 8 to 9 p.m. group were obese, compared to 23 percent of the 9 p.m. or later group.

"For parents, this reinforces the importance of establishing a bedtime routine," said Sarah Anderson, Ph.D., and lead author of the study in an interview with Working Mother. While there are undoubtedly many other factors at play here, this study was the first to follow the effects of late bedtimes on young, preschool-aged children up to 10 years later, as pointed out by Anderson.